1. Field of the Invention
The present invention relates to a socket for electrical parts for detachably accommodating an electrical parts such as a semiconductor device or the like (hereinafter referred to as xe2x80x9cIC packagexe2x80x9d), more particularly relates to a socket for electrical parts capable of easily replacing a contact pin that contacts with or separates from a terminal of the electrical parts.
2. Prior Art of the Invention
Conventionally, an IC socket as a xe2x80x9csocket for electrical partsxe2x80x9d is previously mounted on a circuit board and then accommodates an IC package on the IC socket, achieving an electrical contact between the IC package and the circuit board.
As for the IC packages, for example, those having numbers of terminals on a lower surface of a rectangular type package body have been exemplified.
Each of these terminals of the IC package is brought to electrically contact with said circuit board via each contact pin, by making each of the terminals of the IC package contact with an upper portion of the contact pin in the IC socket while the IC package is held on the IC socket.
As typically shown in FIGS. 21A and 21B, the contact pin 1 comprises an upper end portion 1a that abuts against and contacts with the terminal of the IC package, a lower end portion 1b that abuts against and contacts with the circuit board and an approximately arcuate and elastically deformable elastic portion 1c between the upper portion 1a and the lower portion 1b. 
The upper portion 1a is inserted into an upper through hole 3a formed to a floating plate 3 of the socket body 2 and the lower portion 1b is inserted into an lower through hole 4a formed to a base portion 4 of the socket body 2. The upper and lower portions each contact with the IC package and the circuit board under a prescribed contact pressure respectively, while the elastic portion 1c is elastically deformed. And the contact pin 1 is formed with a projection 1d for preventing the contact pin 1 from dropping out.
In such an IC socket mentioned above, two major processes described below have been conceived when there is a need to replace the contact pin 1.
(1) At first, the base portion 4 and the floating plate 3 are taken apart, and then the contact pin 1 is taken out or inserted.
(2) At first, a damaged contact pin 1 is forcibly taken out without taking apart the base portion 4 and the floating plate 3, and then a new contact pin 1 is forcibly inserted.
The foregoing conventional processes have following disadvantages. That is, in the above mentioned process (1), there is certainly no need to apply too much force in taking out or inserting the contact pin 1. But at the time when the floating plate 3 is made to attach to the base portion 4, the process of inserting all contact pins 1 into the upper through holes 3a of the floating plate 3 must be done, being a difficult process. On the other hand, in the above mentioned process (2), damages may occur at a peripheral portion of the upper through hole 3a of the floating plate 3 at the time the contact pin 1 is forcibly taken out upwardly, and plastic deformation also may occur at the projection 1d at the time when the contact pin 1 is forcibly inserted, because there is the peripheral portion around the upper through hole 3a of the floating plate 3. Therefore, forcible insertion or takeout of the contact pin 1 is a difficult process in replacing the contact pin 1.
Accordingly, when only one or a few contact pins are damaged among numbers of them, the IC socket itself having a damaged contact pin must be replaced with a new one, being inconvenient and expensive.
The processes of this kind are described in Japanese Patent Publication No. Tokkai Hei 6-89764.
An object of the present invention is aimed at substantially eliminating defects or drawbacks encountered in the prior art mentioned above and to provide a socket for electrical parts capable of easily replacing even only one of the contact pins without disassembling the socket body itself.
In order to achieve this or other objects of the present invention, an aspect of the present invention is that a socket for electrical parts comprises:
a socket body on which an electrical part is accommodated; and
a contact pin provided to the socket body,
the contact pin comprising;
an upper end portion to contact with a terminal of the electrical part,
a lower end portion to electrically contact with a circuit board,
an elastically deformable spring portion between the upper end portion and the lower end portion,
an elastic deformation portion formed in the upper end portion, and
an engaging portion formed on an end most portion of the elastic deformation portion,
the socket body comprising;
an upper through hole into which the upper end portion of the contact pin is inserted, and
a lower through hole into which the lower portion of the contact pin is inserted,
the contact pin being able to be installed in the socket body by inserting the lower end portion thereof via the upper through hole into the lower through hole, then inserting the upper end portion thereof into the upper through hole with the elastic deformation portion deformed, and then releasing the deformation of the elastic deformation portion at the time the insertion is completed, finally the engaging portion engaging with a lower surface portion of a peripheral portion of the upper through hole, to prevent the contact pin from being fallen out from the upper through hole.
According to the foregoing aspect of the present invention, elastic deformation at the elastic deformation portion of the contact pin allows the contact pin to be easily driven into or taken out of the socket body without dismantling the socket body, so that even only one of the contact pins can be easily replaced.
Another aspect of the present invention is that a contact surface portion extending in an approximately horizontal direction is provided on the upper end portion to abut against a spherical terminal of the electrical part, and a recess portion is provided on the contact surface portion to prevent a lower end portion of the spherical terminal from abutting against the contact surface portion.
According to the foregoing aspect of the present invention, since the recess portion is provided on the contact surface portion of the contact pin, the lowermost portion of the round shaped terminal of the electrical part is kept from being damaged.
Another aspect of the present invention is that the recess portion of the upper end portion of the contact pin has an ellipsoidal shape elongated in the bending direction of the spring portion.
According to the foregoing aspect of the present invention, when the contact surface portion of the contact pin is urged downwards with the round shaped terminal of the electric part being driven into the ellipsoidal recess of the contact pin, the contact surface portion is displaced. As the ellipsoidal recess is made elongated along the displacement direction, the round shaped terminal moves within the range of the ellipsoidal recess in a relative displacement manner with respect to the recess, resulting in that the displacement is allowed. Therefore, an unnecessary or excessive force does not apply on the round shaped terminal or the contact pin etc. In addition, a wiping effect can be exerted because the round shaped terminal slides within the recess in the relative displacement manner.
Another aspect of the present invention is that the contact surface portion extending in an approximately horizontal direction is provided on the upper end portion to abut against a plane like terminal of the electrical part, and a projection is provided on the contact surface portion to abut against the plane like terminal.
Still another aspect of the present invention is that an inclined guide portion is further provided at the upper peripheral portion of the lower through hole of the socket body, to help guide the lower end portion of the contact pin into the lower through hole.
According to the foregoing aspect of the present invention, the lower end portion of the contact pin can be easily inserted into the lower side through hole since the inclined guide portion is provided at the upper peripheral portion of the lower side through hole.